Vibration isolation arrangement for aperture card photographic copying machine

ABSTRACT

A photographic copying machine is adapted to expose and process a photosensitive film insert on an aperture card, respectively at exposing and processing stations. The machine includes a vibration isolation arrangement for isolating the exposure station and an aperture card, located thereat, from vibration produced by other members of the machine. This permits a relatively long exposure of the film insert without sacrificing image resolution or sharpness.

United States Patent [191 Endter et a1.

-' 51 Mar. 19, 1974 VIBRATION ISOLATION ARRANGEMENT FOR APERTURE CARD PI-IOTOGRAPI'IIC COPYING MACHINE Inventors: Dale S. Endter; Edwin E. Miller,

both of Rochester; Harry L. Westacott, Fairport, all of NY.

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

Filed: Oct. 31, 1972 Appl. No.: 302,433

[52] US. Cl 355/18, 95/14, 355/27,

' v 355/73 Int. Cl. G03b'27/00 Field of Search...; 95/12.5, 14;- 355/18, 27,

References Cited UNITED STATES PATENTS Karnes et al 96/125 2.572.919 10/1951 French et a l 96/125 X 2,506,632 5/1890 Dart 3.233.532

2/1966 Kutchera 95/ l 4 Primary Examiner-Richard M. Sheer [5 7] ABSTRACT A photographic copying machine is adapted to expose and process a photosensitive film insert on an aperture card, respectively at exposing and processing stations. The machine includes a vibration isolation arrangementfor isolating the exposure station and an aperture card, located thereat, from vibration produced by other members of the machine.'This permits a relatively long exposure of the film insert without sacrificing image resolution or sharpness.

5 Claims, 5 Drawing Figures PAIENTEDMAR 19 m4 SHEET 1 0F 3 FIG! PATENIEU m 1 9 m4 SHEET 3 [IF 3 vIBRATtoNIsoLAnoN ARRANGEMENT FOR APERTURE CARD PHOTOGRAPHIC COPYING MACHINE CROSS REFERENCE TO RELATED APPLICATIONS Reference is made to commonly assigned copending' U.S. Patent Application Ser. No. 302,432 entitled ALIGNMENT STATION FOR APERTURE CARD PHOTOGRAPHIC COPYING MACHINE and filed in the manes of Dale S. Endter and Edwin E. Miller on Oct. 31, 1972. Reference is further made to commonly assigned copending U.S. Patent Application Ser. No. 300,922 entitled DOCUMENT HOLDER EX- CHANGE APPARATUS and filed in the names of Louis C. Nosco and James E. Ryan on Oct. 26, I972.

I BACKGROUND OF THE INVENTION The present invention relates to a photographic copying machine in whichan aperture card with a photosensitive film insert is moved to successively arranged exposing and processing stations for exposing and processing of such film insert. More particularly, the invention relates to means for isolating the exposing station and an aperture card, located thereat, from vibration.

U.S. Pat. No. 3,181,449 issued on May 4, I965 to Wright and U.S. Pat. No. 3,233,532 issued on Feb. 8, 1966 to Kutchera relate to photographic copying machines adapted to expose a film insert on an aperture card and to process such exposed film. In a photographic copying machine to which the present invention is directed, an indexable turntable, such as a rotatable index table or dial, supports a plurality of card holding members each of which carries an aperture card. The dial is indexed for movement to successive positions to bring each card holding member, in turn, into operative cooperation with different machine stations. For example, in a six station machine, in which the dial indexes through 60 rotational increments, the first station supplies an aperture card to the correspondingcard holding member, the second station accurately positions the card relative to the holder, the third station exposes the film frame on such card with a reduced size image of the material being copied, the fourth and fith stations respectively develop and stop, and fix and wash the exposed film, and the sixth station dries the processed film and discharges the card from the machine. Since all of these stations perform their respective functions following each indexing movement of the dial, such a machine is capable of making six aperture card photocopies during each complete revolution of the dial.

Because the film insert on an aperture card is of much smaller area than the material being copied, the image formed on the film insert'at the third station must be of correspondingly high resolution to preserve small details of the copied material. In copying medical radiographs or X-rays, for example, the preferred resolution of the forward image must be at least in excess of one hundred lines per millimeter to provide the required degree of detail. This high degree of resolution and the correspondingly long exposure time required, which is typically on the order of several seconds or more, makes it essential to prevent any relative movement between the film insert, the optical system and the copied material during the exposure of the film. In previously known machines of this general type, however, it has not been possible to achieve this order of resolution consistently under normal operating conditions because of mechanical vibration inherent in the machine.

SUMMARY OF THE INVENTION A principle object of the present invention is to provide a vibration isolation arrangement in a photographic copying machine.

A concomitant object of the present invention is to accomplish the foregoing object purpose bysimple and reliable means which are functionally independent of the overall structural rigidity of such machine.

Briefly, these and other related objectives are accomplished in accordance with a preferred embodiment of the present invention by utilizing spring means to attach the individual card holder members to the indexable dial of a machine of the general type previously described, and by combining both the optical system and a copy board that supports the original material in a unitary camera structure that is resiliently mounted to the frame of the machine. During the film exposure operation, the camera structure and the corresponding card holder are urged into mating engagement with each other to prevent any relative movement therebetween and the mated card holder and camera structure is effectively isolated from induced vibration by the absence of any non-resilient connection between those components and the remainder of the machine.

Various means for practicing the invention and other advantages and features thereof will be apparent from the following detailed description of an illustrative preferred embodiment of the invention, reference being made to the accompanying drawings in which like reference characters denote like elements.

In the drawings:

FIG. .1 is a somewhat simplified perspective view of a six station aperture card photographic copying machine which incorporates the present invention;

FIG. 2 is a partially cross sectioned viewed taken along the line 2-2 of FIG. '1;

FIG..3 is aperspective view of an aperture card that can be used in the six-station machine;

FIG. 4 is a perspective underside view'of one of six identical card holders embodied in the illustrative machine; and

FIG. 5 is a partially cross sectional view of the card holder shown in FIG. 4, taken along the offset line 5--5 of that figure and showing the card holder in mating engagement with an exposing station.

DESCRIPTION OF THE ILLUSTRATIVE PREFERRED EMBODIMENT Referring first to FIG. 1 of the accorn anying drawings, anillustrative photographic copy'ng machine incorporating the present invention inc udes a frame 11 supporting a gearbox 12 having a otatable vertical shaft 13 that carries a circular turnt ble or dial 14. Six identical aperture cardholders 15 are symmetrically spaced about an undersurface of t e dial 14. The dial is mounted for horizontal rotatio through successive increments and for vertical m vement at the completion of each such increment, t bring the card holders into superposed alignment espectively with six symmetrically spaced operating stations 16-21 fixed to the frame 11 or to the gearbox 12. Although omitted in the drawings for purpose of clarity, the illustrated machine is enclosed in an external housing or cabinet that excludes ambient light from aperture cards individually carried by the card holders 15.

The gearbox 12 is best illustrated in FIG. 2 and includes a housing 22 provided with bushings 23 which support the dial shaft 13 both for horizontal rotation and also for vertical movement. A countershaft 24 is rotatably supported, parallel to the dial shaft 13, by bushings 25 and is connected to an intermittently operated gear reduction motor 26. A switching device (not shown), disclosed in commonly assigned copending U.S. Patent Application Ser. No. 302,432 (more specifically referenced hereinbefore), is adapted to control the motor 26 in a manner such that each time the motor is energized the countershaft 24 is rotated through a single 360 revolution and then stops with the dial shaft 13 at the depicted vertical position. The countershaft 24 is connected to the dial shaft 13 by a generally conventional Geneva drive unit having a driving wheel 37 on the countershaft and a six position indexing wheel 28 on the dial shaft; whereby each complete 360 revolution of the countershaft causes the dial 14 to rotate through a partial 60 revolution and to stop with the six card holders 15 in vertical alignment respectively with the six operating stations 16-21.

A driving pin 29 and a blocking hub 30 of the driving wheel 27 are of sufficient length to enable vertical movement of the dial shaft 13, the dial 14 and the card holders 15 from their illustrated lowered position to a raised position (not shown) at which the card holders are lifted from the operating stations 16-21 (but still aligned therewith). This vertical movement of the dial shaft 13 and the dial 14 is accomplished by a lever 31 pivotally connected, at one end, to the gearbox housing 22 by a pin 32. A roller 33 at an opposite end of the lever 31 rides in an annular slot 34 in the dial shaft 13 and a second roller 35 near the center of the lever is received in an annular cam slot 36 defined by opposed end faces of two barrel cam sleeves 37 and 38 on the countershaft 24. As the countershaft 24 begins to rotate, the cam slot 36 moves the roller 35 upwardly and thereby lifts the dial 14 to the raised position before the driving pin 29 enters one of six driving slots 39 in the indexing wheel 28 to effect indexing rotation of the dial through a 60 increment. After the dial 14 has been so rotated, the cam slot 36 causes the lever 31 to lower the dial to the lowered position and thereby seats the six card holders 15 in engagement respectively with the six operating stations 16-21, as described later with reference to FIGS.4 and 5.

FIG. 3 illustrates an aperture card 41, which may be employed in the illustrative machine. As is well known in the art, such a card includes a generally rectangular sheet portion 42 of relatively stiff paper or cardboard having a rectangular opening or aperture 43 across which is disposed a photographic film insert 44. A stack of these cards 41 is placed in a card loading station 16 of the machine and the topmost card is picked-up by a different one of the card holders 15 during a respective operating cycle. After a picked-up card has been positioned in a certain relation to the card holder therefor, at an alignmentstation 17 the details of which are disclosed in commonly assigned copending U.S. Patent Application Ser. No. 302,432, the film insert 44 on such card is exposed at an exposing station 18 and thereafter developed and stopped at a first processing station 19, fixed and washed at a second processing station 20 and dried and discharged from the machine at an exit station 21.

Referring now to FIGS. 4 and 5, each of the six identical card holders 15 has an upper, support plate 45 which is mounted to the undersurface of the dial 14 by several screws 46. A lower, card holding platen 47 is suspended from the support plate 45 by four, evenly spaced, helical compression springs 49. These springs 49 have their respective opposite ends secured to the platen 47 and the support plate 45, by means of several projections 50 on the platen and the support plate. Moreover, these springs are of the same strength and size. When a card holder 15 is in engagement with any one of the operating stations 16-21, the springs 49 will be compressed due to movement of the support plate 45 toward the platen 47 as the dial 14 is finally lowered to the lowered position. As shown in FIGS.4 and 5, the support plate 45 and the platen 47 have a plurality of L-shaped members 51 and 52, respectively, which couple or engage to establish a maximum distance of separation between the support plate and the platen when the springs are not compressed and which uncouple or disengage, permitting compression of the springs, as the card holder is moved into engagement with the operating station.

The underside of the platen 47 is stepped to provide a card supporting surface 55 and a recessed surface 56. A pair of suction cups 57 and a pair of brackets 53 are mounted on the platen surface 56. The suction cups 57 are connected by a flexible vacuum line 58 to any one of six identical valves 59, on the dial 14, which selectively controls evacuation of air from the suction cups (see FIGS.1 and 4). Although not described hereinafter, the valves 59 are disclosed in detail in commonly assigned copending U.S. Patent Application Ser. No. 302,432. The card grasping faces of the suction cups 57 and top faces 54 of the brackets 53 are disposed in substantially coplanar relation with the platen surface 55, and serve to hold an aperture card 41 adjacent that surface with the film insert 41 aligned with a central film holding surface 61 of the platen. At opposite longitudinal edges of the held aperture card, two guide pins 68 project downwardly from the platen 47. As shown in FIG. 5, which illustrates a card holder 15 in engagement with the exposing station 18, the two guide pins 62 are separately received in two guide bushings or openings 69 in that station. The pins 68 and the bushings 69 serve to mate and thereby accurately align the platen 47 with the exposing station 18. It is to be understood that each of the six operating stations 16-21 is provided with these bushings to effect similar engagement of the six card holders 15 respectively with such stations. Because the springs 49 are the only means interconnecting the support plate 45 and the platen 47, the platen can be moved in a lateral manner relative to the support plate to accommodate for inaccuracies in the alignment of the support plate with any one of the operating stations 16-21.

Referring again to FIGS. 1 and 2, the exposing station 18 includes a unitary camera structure 71 having a head member 72 rigidly connected to a tapered enclosure 73 that extends upwardly from a box-like copyboard housing 74. As shown most clearly in FIG. 2, two opposed resilient rubber support members 75 suspend the copyboard housing 74 from two brackets 76 fixed to the machine frame 11. Moreover a'resilient rubber member 77 suspends to camera head member 72 from a frame bracket 78 fixed to the frame 11. Thus, the exposing station 18 is free on all sides except at three points .of support respectively established by the support members 75 and 77, to provide a resilient threepoint suspension that maintains the camera structure 71 accurately in a predetermined vertical position and in vibration isolation from the machine frame 11.

A lower wall 79 of the copyboard housing 74 is provided with a wide slot 81 adapted to be spanned by a copyboard assembly 82 which may be of any suitable construction. This assembly 82, shown by way of example, includes a frame 83 holding a flat glass plate 84 on which is placed a radiograph 85 or similar light transmissive material to be copied. A lateral opening 86 in the copyboard housing 74, shown in FIG.1, is aligned with a rigidly supported tray 87 that supports the copyboard assembly 82 when such assembly is slid out of the copyboard housing 74 to permit replacement of any copied material with uncopied material. Preferably, the machine employs two interchangeable copyboard assemblies, one of them being reloaded while the other is positioned in the machine. Such an assembly interchange is disclosed in commonly assigned copending US. Patent Application Ser. No. 300,922 (more-specifically referenced hereinbefore). When the copyboard assembly 82 is located within the copyboard housing 74, such assembly is positioned directly above an opentop lamp housing 88 rigidly supported by the machine frame 1 1 and below but out of physical contact with the camera structure 71. Typically, the lamp housing 88 encloses a plurality of parallel extending tubular lamps 89, but other types of light sources could obviously be substituted. If the machine is to be used for copying opaque rather than light transmissive material, appropriate illumination means would be incorporated within the camera structure itself as represented in broken lines by two lamps 91.

The head member 72 of the camera'st'ructure 71 supports an objective lens system 92 below an electrically,

operated shutter 93 aligned with a rectangular exposure opening 94 in an upper head wall 95. When an aperture card 4lis sandwiched between the platen 47 of a card holder 41 is and the flat top surface 96 of a rib 97 surrounding the exposure opening 94, as best shown in FIG. 5, the film insert 44 on such card is aligned accurately with the exposure opening. Moreover, the film insert 44 is held in a flat horizontal plane, in contact with the central film holding surface 61 on the platen 47, by the application of a vacuum through small openings (not shown) in the platen and the film holding surface. At this time, the springs 49 serve to squeeze the sheet portion 42 of the card 41, immediately surroundi ing the film insert 44, against the rib surface 96. The

plane of the emulsion film surface is thereby located in accurate coincidence with the image plane of the lens system 92 focused on any material being copied to provide a high resolution photograph when the shutter 93 is operated. It will be noted, in FIG. 2, that the mated I respectivelyto the shutter 93 and to the lamps 91, and a flexible boot or bellows (not shown) or the equivalent can be associated with the camera structure 71 for light sealing purposes, but such flexible members obviously do not prejudice the vibration isolation of the camera structure 71. Since the shutter 93 operates relatively slowly, the amount of vibration produced thereby is negligible, but the shutter can be eliminated entirely, if desired, by controlling the exposure duration through timed energizationof the light source.

After thefilm insert 44 on theaperture card 41 has been exposed, such card'is carried by a card holder 15 to the first processing station 19 where the card is sandwiched between the platen 47 of that holder and a rib of a processing plate (not shown) having an opening through which develop and stop processing fluids are delivered in sequence to a lower face of the film insert. This rib is similar in construction to the rib 97, shown in FIG. 5, surrounding the exposure opening 94. At the second processing station 20, the same kind of operation is repeated with fix and wash processing fluids. To allow the emulsion on the film insert 44 to be compltely flooded by the processing fluids without danger of those fluids escaping and wetting more of the sheet portion 42 of the card 41 than an area immediately surrounding the film insert 44, the platen 47 must squeeze such card area against the ribs of the processing station 19 and 20 with substantially more spring force than is exerted by the four springs 49. Therefore, the card contacting surfaces of the processing stations 19 and 20 are located at a higher elevation than that of the corresponding surface of the exposing station 18; whereby housing of the dial 14 to the lowered position causes the support plate 45 of the card holder 15 not only to compress the springs 49 but further to compress a substantially stronger and larger helical compression spring 101, shown in FIGS. 2 and 5, which serves no function except at the processing stations. As shown in FIG. 5,-each one of the card holders 15 has a stud 102 fixed to and projecting from the platen 47 and loosely seating the spring 10l.The spring 101 is centrally locatedbetween the springs 49 and serves to squeeze the aforementioned card area firmly against the ribs of the processing stations 19 and 20.

Following the washing operation, the final indexing rotation and vertical movement of the dial 14 brings the processed card to the exit station 21, where such card is dried by heated air before released by the vacuum cups 57 and discharged into an appropriate chute or receptacle.

Although the present invention has been illustrated in use with aperture cards, it will be appreciated that the invention can similarly be used with other photopraphic material such as film sheets.

The invention has been described in detail with particular reference to an illustrative preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. An improved photographic apparatus of the kind for exposing a photosensitive medium, wherein a platen is provided for carrying a photosensitive medium, wherein an exposing station including a camera structure is provided for exposing a photosensitive medium carried by said platen, wherein means is provided for moving said platen and the carried medium relative to said exposing station into an exposing position on said station, wherein a frame is provided for supporting said exposing station and said platen moving means, and wherein the improvement comprises:

first resilient means interconnecting said camera structure and said frame in a manner such that said camera structure is free on all sides except respective points of support established by said resilient means, for isolating said camera structure from any vibration of said frame; and

second resilient means interconnecting said platen and said platen moving means, for holding said platen and the carried medium in said exposing position and, at the same time isolating said platen and the carried medium from any vibration of said frame said second resilient means including a plurality of compression springs having opposite ends respectively connected to said platen and said platen moving means, and disposed for compression in respone to movement of said platen into said exposing position on said exposing station.

2. The improvement as recited in claim 1, further comprising:

first and second engageable means respectively fixed to said platen and said platen moving means for coupling said platen and said platen moving means to effect a maximum distance of separation therebetween and for uncoupling said platen and said platen moving means, in response to movement of said platen onto said exposing station, to enable compression of said springs.

3. An improved photographic apparatus of the kind for exposing a photosensitive medium, wherein a platen is provided for carrying a photosensitive medium, wherein an exposing station including a camera structure is provided for exposing a photosensitive medium carried by said platen, wherein means is provided for moving said platen and the carried medium to said exposing station into an exposing position on said station and for moving said platen and the carried medium from said exposing station, wherein a frame is provided for supporting said exposing station and said platen moving means, and wherein the improvement comprises: I

resilient means interconnecting said camera structure and said frame in a manner such that said camera structure is free on all sides except respective points of support established by said resilient means, for isolating said camera structure from any vibration of said frame;

a plurality of compression springs having opposite ends respectively connected to said platen and said platen moving means in a manner separating said platen from said platen moving means, and disposed for enabling generally lateral movement of said platen relative to said platen moving means and for compression in response to movement of said platen into said exposing position; and

first and second engageable means respectively fixed to said platen and said exposing station for engagement, in response to movement of said platen into said exposing position, to effect registration of said platen and the carried medium with said exposing station and for disengagement to enable movement of said platen and the carried medium from said exposing station.

4. The improvement as recited in claim 3, wherein said first and second engageable means includes:

a plurality of pins depending from said platen; and

means defining a plurality of openings in said exposing station for respectively receiving said pins as said platen is moved into said exposing position.

5.. An improved photographic copying machine of the kind for exposing and processing a photosensitive film insert mounted in the aperture of an aperture card, wherein a platen is provided for carrying an aperture card, wherein exposing and processing stations are provided below said platen for exposing and processing a film insert of an aperture card carried by said platen, wherein means including an index table is provided for lowering said platen and the carried card into exposing and processing positions respectively on said exposing and processing stations and for raising said platen and the carried card from said exposing and processing stations, wherein a frame is provided for supporting said exposing and processing stations and said platen moving means, and wherein the improvement comprises:

resilient means interconnecting said exposing station and said frame in a manner such that saidexposing station is free on all sides except respective points of support established by said resilient means, for isolating said exposing station from any vibration of said frame;

a plurality of first compression springs having opposite ends respectively connected to said platen and said index table in a manner suspending said platen from said index table, and disposed for enabling generally lateral movement of said platen relative to said index table and for compression in response to lowering of said platen into said exposing and processing positions;

a plurality of pins depending from said platen;

means defining a plurality of openings in said exposing and processing stations for individually receiving one of said pins as said platen is lowered respectively into said exposing and processing positions; and

a second compression spring having opposite ends respectively disposed on said platen and spaced from said index table, said second compression spring exerting a greater compression force than such force exerted by said plurality of first compression springs. 

1. An improved photographic apparatus of the kind for exposing a photosensitive medium, wherein a platen is provided for carrying a photosensitive medium, wherein an exposing station including a camera structure is provided for exposing a photosensitive medium carried by said platen, wherein means is provided for moving said platen and the carried medium relative to said exposing station into an exposing position on said station, wherein a frame is provided for supporting said exposing station and said platen moving means, and wherein the improvement comprises: first resilient means interconnecting said camera structure and said frame in a manner such that said camera structure is free on all sides except respective points of support established by said resilient means, for isolating said camera structure from any vibration of said frame; and second resilient means interconnecting said platen and said platen moving means, for holding said platen and the carried medium in said exposing position and, at the same time isolating said platen and the carried medium from any vibration of said frame said second resilient means including a plurality of compression springs having opposite ends respectively connected to said platen and said platen moving means, and disposed for compression in respone to movement of said platen into said exposing position on said exposing station.
 2. The improvement as recited in claim 1, further comprising: first and second engageable means respectively fixed to said platen and said platen moving means for coupling said platen and said platen moving means to effect a maximum distance of separation therebetween and for uncoupling said platen and said platen moving means, in response to movement of said platen onto said exposing station, to enable compression of said springs.
 3. An improved photographic apparatus of the kind for exposing a photosensitive medium, wherein a platen is provided for carrying a photosensitive medium, wherein an exposing station including a camera structure is provided for exposing a photosensitive medium carried by said platen, wherein means is provided for moving said platen and the carried medium to said exposing station into an exposing position on said station and for moving said platen and the carried medium from said exposing station, wherein a frame is provided for supporting said exposing station and said platen moving means, and wherein the improvement comprises: resilient means interconnecting said camera structure and said frame in a manner such that said camera structUre is free on all sides except respective points of support established by said resilient means, for isolating said camera structure from any vibration of said frame; a plurality of compression springs having opposite ends respectively connected to said platen and said platen moving means in a manner separating said platen from said platen moving means, and disposed for enabling generally lateral movement of said platen relative to said platen moving means and for compression in response to movement of said platen into said exposing position; and first and second engageable means respectively fixed to said platen and said exposing station for engagement, in response to movement of said platen into said exposing position, to effect registration of said platen and the carried medium with said exposing station and for disengagement to enable movement of said platen and the carried medium from said exposing station.
 4. The improvement as recited in claim 3, wherein said first and second engageable means includes: a plurality of pins depending from said platen; and means defining a plurality of openings in said exposing station for respectively receiving said pins as said platen is moved into said exposing position.
 5. An improved photographic copying machine of the kind for exposing and processing a photosensitive film insert mounted in the aperture of an aperture card, wherein a platen is provided for carrying an aperture card, wherein exposing and processing stations are provided below said platen for exposing and processing a film insert of an aperture card carried by said platen, wherein means including an index table is provided for lowering said platen and the carried card into exposing and processing positions respectively on said exposing and processing stations and for raising said platen and the carried card from said exposing and processing stations, wherein a frame is provided for supporting said exposing and processing stations and said platen moving means, and wherein the improvement comprises: resilient means interconnecting said exposing station and said frame in a manner such that said exposing station is free on all sides except respective points of support established by said resilient means, for isolating said exposing station from any vibration of said frame; a plurality of first compression springs having opposite ends respectively connected to said platen and said index table in a manner suspending said platen from said index table, and disposed for enabling generally lateral movement of said platen relative to said index table and for compression in response to lowering of said platen into said exposing and processing positions; a plurality of pins depending from said platen; means defining a plurality of openings in said exposing and processing stations for individually receiving one of said pins as said platen is lowered respectively into said exposing and processing positions; and a second compression spring having opposite ends respectively disposed on said platen and spaced from said index table, said second compression spring exerting a greater compression force than such force exerted by said plurality of first compression springs. 